Low liquid level shut-off apparatus for gas burner



' Dec. 26, 1967 J. 5. CAROTHERS LOW LIQUID LEVEL SHUT-OFF APPARATUS FOR GAS BURNER Filed Aug. 22, 1966 I INVENTOR- john 5. arofkens Affomggs United States Patent 3,359,972 LOW LIQUID LEVEL SHUT-OFF APPARATUS FOR GAS BURNER John S. Carothers, Birmingham, Ala., assignor to Alabama Gas Corporation, a corporation of Alabama Filed Aug. 22, 1966, Ser. No. 574,013 4 Claims. (Cl. 126-374) ABSTRACT OF THE DISCLOSURE Control apparatus for gas supply line to a burner heating liquid in an open vessel in which a valve in the supply line is moved toward and away from closed position by the forces of spring means and gas pressure in the supply line in response to decreases and increases in pressure in a dip tube extending downwardly into the vessel.

This invention relates to low liquid level shut-off apparatus for a gas burner and more particularly to means for closing a gas supply line to a burner for heating a liquid in a vessel in response to the liquid in the vessel dropping to a predetermined level.

An object of my invention is to provide low liquid level shut-off apparatus for a gas burner of the character designated in which the gas supply line is closed directly in response to a predetermined drop in liquid level, thereby eliminating the necessity of providing electrical current, or complicated electrical controls, bulky floats and the like.

A more specific object of my invention is to provide a low liquid level shut-off device for a gas burner of the character designated which shall be particularly adapted for use with a sink, such as the type employed to wash dishes and cooking utensils, thus preventing damage to the sink and the contents thereof due to overheating a dry sink.

Another object of my invention is to provide low liquid level shut-off apparatus for a gas burner of the character designated which is adapted to open the gas supply line to the burner when the liquid level is raised to a predetermined level.

A further object of my invention is to provide low liquid level shut-off apparatus for a gas burner of the character designated which modulates the gas input at liquid levels between gas shut-off level and a predetermined higher level at which full input of gas is obtained whereby reduced gas input is provided at very low levels and higher gas input is provided at higher levels.

A further object of my invention is to provide low liquid level shut-off apparatus of the character designated which shall be extremely simple of construction, economical of manufacture and one which is sanitary in every respect.

As is well known in the art to which my invention relates, ditficulties have been encountered in providing effective low liquid level shut-off means for sinks employed to wash dishes and cooking utensils due to the fact that any control means positioned within the sink must be free of any recesses, cavities or the like in which residual deposits can collect over a period of time. That is, all surfaces of the control mechanism must be accessible for a thorough cleaning in an efiicient manner. Difiiculties have also been encountered due to the fact that the control means for shutting off the gas supply must operate independently of the heat of the solution being heated whereby the gas supply is cut off immediately upon a predetermined drop in liquid level regardless of the temperature thereof.

To overcome the above and other difiiculties, I provide a valve housing in the gas supply line having a valve which is adapted to move selectively from a closed, seated position to an open position. A first diaphragm is operatively connected to the valve and defines a seal for one side of the valve housing. A second diaphragm is operatively connected to the valve and spaced from the first mentioned diaphragm to define a closed chamber therebetween. A tap passageway communicates the closed chamber with the gas inlet for the housing whereby the gas pressure at the gas inlet exerts force to aid in closing the valve. Spring means is provided for urging the valve toward and away from closed position and a second closed chamber is provided at the opposite side of the second mentioned diaphragm from the first mentioned closed chamber. Communicating with the second closed chamber is a conduit having a depending dip tube at the lower end thereof which is disposed to extend downwardly into the liquid in the vessel and trap air within the dip tube so that pressure is increased and decreased within the second mentioned closed chamber in response to a rise and fall, respectively in the liquid level in the vessel being heated.

Apparatus embodying features of my invention is illustrated in the accompanying drawing, forming a part of this application, in which:

FIG. 1 is a vertical sectional view through the valve housing showing the manner in which the conduit for the dip tube is connected thereto;

FIG. 2 is a vertical sectional view through a sink, drawn to a smaller scale, showing my improved apparatus associated therewith, and,

FIG. 3 is a fragmental view showing a gas supply line having a thermostat control valve therein and my improved low liquid safety valve therein.

Referring now to the drawing for a better understanding of my invention, I show a sink 10, such as a conventional type sink employed to wash dishes, cooking utensils and the like. The sink is heated by a gas burner 11 which is connected to a gas supply line 12. The water W in the sink 10 is maintained at a desired temperature by a thermostat controlled valve 13. The valve 13 is connected to a thermostat indicated at 14 which is mounted on the side of the sink 10, as shown in FIG. 2.

My improved apparatus for closing the gas supply line 12 in response to the liquid in the sink 10 dropping to a predetermined level comprises a valve housing 16 having a gas inlet 17 and a gas outlet 18. A valve 19 is provided in the housing 16 in position to cooperate with a valve seat 21 whereby the valve 19 is moved selectively from a closed, seated position to an open position. A valve stem 22 is formed integrally with the valve 19, as shown in FIG. 1. A diaphragm 23 is carried by the valve stem 22 and is secured to the housing 16 to define a seal for one side thereof. A second diaphragm 24 is carried by the valve stem 22 in spaced relation to the diaphragm 23 to define a closed chamber 26 therebetween. A tap passageway 27 communicates the closed chamber 26 with the gas inlet 17 whereby the gas pressure at the inlet 17 exerts a force to increase the pressure within the chamber 26 and thus aid in closing the valve 19. v

An adjustable spring unit 28 is mounted at the opposite side of the diaphragm 24 from the closed chamber 26 in position to urge the valve stem toward open position. A counter spring 29 is interposed between the valve 19 and the inner surface of the housing 16, as shown in FIG. 1, whereby the spring 29 urges the valve 19 toward closed position.

The diaphragm 24 is spaced from the lower portion of the housing 16 to define a second closed chamber 31 therebetween which is at the opposite side of the diaphragm chamber 31, as shown in FIG. 1. Communicating with the passageway 32 is the upper end of a conduit 33 which is threadedly connected to the housing 16, as shown. The lower end of the conduit 33 is secured to the upper end of a depending dip tube 34 having an opened lower end 36. The internal, cross sectional area of the dip tube 34 is greater than the internal cross sectional area of conduit 33.

From the foregoing description, the operation of my improved apparatus will be readily understood. With no liquid, such as water, in the sink 10, the valve 19 is held closed by the counter spring 29 and the build-up of pressure within the closed chamber 26 due to the tap passageway 27 which communicates the chamber 26 with the gas inlet 17. Upon adding liquid to the sink 10, the liquid level rises to thus trap air within the dip tube 34. This air is compressed by the upwardly moving liquid within the dip tube 34. The build up of pressure within the dip tube 34 exerts a force on the under side of the diaphragm 24, as viewed in FIG. 1, due to the increase of pressure within the closed chamber 31. This increase in pressure within the closed chamber 31 overcomes the pressure exerted by the gas through tap passageway 27 and the force exerted by the counter spring 29 to thus force the valve 19 to openposition whereupon the gas flows through the supply line 12 and the valve housing 16 in the direction of the arrows. The apparatus is thus adapted to reopen the gas supply line to the burner, after being shut off, when the water level is raised by admitting more water to sink 10.

In the event the sink is drained or for some reason the water leaks out or is evaporated to a predetermined lower level, the pressure within the dip tube 34 and the closed chamber 31 is reduced whereupon the valve 19 is then forced to seated position by the force exerted by counter spring 29 and the build up of pressure within the closed chamber 26 through tap passageway 27. The predetermined level at which the valve 19 is closed may be readily adjusted by means of a suitable adjusting nut 37 which increase or decrease the tension applied by the spring '28 in a manner well understood in the art.

The apparatus also modulates the gas input at liquid levels between gas shut-off level and a predetermined higher level at which full input is obtained. That is, reduced gas input is provided at very low levels and higher gas input is provided at higher liquid levels.

From the-foregoing, it will be seen that I have devised an improved apparatus for closing a gas supply'line to a burner immediately upon the liquid level in the vessel dropping to a predeter-minedpoint. By providing a low liquid level shut-off unit which directly controls the operation of the shut-off valve, I eliminate entirely the necessity of providing an electrical current to the shut-ofl? valve or complicated electrical controls, bulky floats and the like. Furthermore, by providing a low liquid level shutoff unit which has a smooth, continuous exterior surface, the unit may be kept in a clean and sanitary condition at all times with a minimum of eifort. Furthermore, by providing a low liquid level shut-01f unit which operates entirely by a differential in pressure created by the rise and fall in liquid level within the vessel, my improved apparatus may be readily applied to conventional type sinks without modification of the sinks in any way.

While I have shown my invention in but one 'form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing trorn the spirit thereof,

and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

1. In combination, a vessel open to the atmosphere and adapted to contain a liquid to be heated, a burner for heating the liquid, and a gas supply line to the burner,

(a) a valve housing in said gas supply line having a gas inlet and a gas outlet and having a valve therein disposed to move selectively from a closed, seated position to an open position,

(b) a valve stem connected to said valve,

(c) a first diaphragm carried by said valve stem and defining a seal for one side of the Valve housing,

(d) a second diaphragm carried by said valve stem and spaced from said first diaphragm to define a closed chamber therebetween,

(e) there being a tap passageway communicating said closed chamber with the gas inlet so that the gas pressure at said inlet exerts a force to aid in closing said valve,

(f) adjustable spring means urging said valve toward open position,

(g) counter spring means urging said valve toward closed position,

(h) a second closed chamber at the opposite side of said second diaphragm from the first mentioned closed chamber,

(i) a conduit communicating with said second closed chamber, and

(j) a depending dip tube having a lower open end and communicating at its upper end with the lower end of said conduit in position to extend downwardly into the liquid in said vessel and trap air within said dip tube so that pressure is increased and decreased within said second closed chamber in response to a rise andfall, respectively, in the liquid level in said vessel, whereby above a predetermined liquid level in the vessel pressure within said second chamber overcomes the pressure of the inlet gas and the force exerted by said counter spring to open said valve and below said predetermined level in the vessel pressure is reduced within said second chamber and the pressure of the inlet gas and the force exerted by said counter spring closes said valve.

2. The combination as defined in claim 1 in which the vessel is a sink which is maintained at a predetermined temperature by a thermostat controlled valve.

3. The combination as defined in claim 1 in which the internal, cross sectional area of the dip tube is greater than the internal cross sectional area of said conduit.

4. The combination as defined in claim 1 in which the forces of said adjustable spring means, said counter spring means and the gas pressure are so selected relative to the pressure produced in said dip tube to modulate the gas input at liquid levels between gas shut-off level and a predetermined higher level to reduce gas input at low levels and increase gas input at higher levels.

References Cited UNITED STATES PATENTS 1,780,996 11/1930 Carroll 126-374 3,101,897 8/1963 Vaughn l58119X JAMES W. WESTHAVER, Primary Examiner, 

1. IN COMBINATION, A VESSEL OPEN TO THE ATMOSPHERE AND ADAPTED TO CONTAIN A LIQUID TO BE HEATED, A BURNER FOR HEATING THE LIQUID, AND A GAS SUPPLY LINE TO THE BURNER, (A) A VALVE HOUSING IN SAID GAS SUPPLY LINE HAVING A GAS INLET AND A GAS OUTLET AND HAVING A VALVE THEREIN DISPOSED TO MOVE SELECTIVELY FROM A CLOSED, SEATED POSITION TO AN OPEN POSITION, (B) A VALVE STEM CONNECTED TO SAID VALVE, (C) A FIRST DIAPHRAGM CARRIED BY SAID VALVE STEM AND DEFINING A SEAL FOR ONE SIDE OF THE VALVE HOUSING, (D) A SECOND DIAPHRAGM CARRIED BY SAID VALVE STEM AND SPACED FROM SAID FIRST DIAPHRAGM TO DEFINE A CLOSED CHAMBER THEREBETWEEN, (E) THERE BEING A TAP PASSAGEWAY COMMUNICATING SAID CLOSED CHAMBER WITH THE GAS INLET SO THAT THE GAS PRESSURE AT SAID INLET EXERTS A FORCE TO AID IN CLOSSAID VALVE, (F) ADJUSTABLE SPRING MEANS URGING SAID VALVE TOWARD OPEN POSITION, (G) COUNTER SPRING MEANS URGING SAID VALVE TOWARD CLOSED PORTION, (H) A SECOND CLOSED CHAMBER AT THE OPPOSITE SIDE OF SAID SECOND DIAPHRAGM FROM THE FIRST MENTIONED CLOSED CHAMBER, (I) A CONDUIT COMMUNICATING WITH SAID SECOND CLOSED CHAMBER, AND (J) A DEPENDING DIP TUBE HAVING A LOWER OPEN END AND COMMUNICATING AT ITS UPPER END WITH THE LOWER END OF SAID CONDUIT IN POSITION TO EXTEND DOWNWARDLY INTO THE LIQUID IN SAID VESSEL AND TRAP AIT WITHIN SAID DIP TUBE SO THAT PRESSURE IS ENCREASED AND DECREASED WITHIN SAID SECOND CLOSED CHAMBER IN RESPONSE TO A RISE AND FALL, RESPECTIVELY, IN THE LIQUID LEVEL IN SAID VESSEL, WHEREBY ABOVE A PREDETERMINED LIQUID LEVEL IN THE VESSEL PRESSURE WITHIN SAID SECOND CHAMBER OVERCOMES THE PRESSURE OF THE INLET GAS AND THE FORCE EXERTED BY SAID COUNTER SPRING TO OPEN SAID VALVE AND BELOW SAID PREDETERMINED LEVEL IN THE VESSEL PRESSURE IS REDUCED WITHIN SAID SECOND CHAMBER AND THE PRESSURE OF THE INLET GAS AND THE FORCE EXERTED BY SAID COUNTER SPRING CLOSES SAID VALVE. 